Stent delivery catheter with bumpers for improved retention of balloon expandable stents

ABSTRACT

An improved balloon catheter which includes bumpers located adjacent to the proximal and distal ends of the catheter balloon. The bumpers form a recessed pocket into which a stent crimped onto the catheter balloon is mounted. The recessed pocket formed by the bumpers securely retains the stent on the balloon and minimizes undesired contact between the stent and arterial walls and lesions during advancement of the stent within a patient&#39;s vasculature.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the field of stent deliverysystems generally, and more particularly to features for improving stentsecurity on balloon dilatation catheters for use in percutaneoustransluminal angioplasty (“PTA”) and percutaneous transluminal coronaryangioplasty (“PTCA”).

[0002] In a typical PTCA procedure a guiding catheter having a preformeddistal tip is percutaneously introduced through the femoral artery intothe cardiovascular system of a patient in a conventional Seldingertechnique and advanced within the cardiovascular system until the distaltip of the guiding catheter is seated in the ostium of the desiredcoronary artery. A guidewire is positioned within an inner lumen of adilatation catheter and then both are advanced through the guidingcatheter to its distal end. The guidewire is first advanced out of thedistal end of the guiding catheter into the patient's coronaryvasculature until the distal end of the guidewire crosses an arteriallesion. Subsequently, the dilatation catheter having an inflatableballoon on its distal portion is advanced into the patient's coronaryanatomy over the previously advanced guidewire until the dilationballoon is properly positioned across the lesion. Once properlypositioned the balloon is inflated, with radiopaque liquid at highpressure (about 4-6 atmospheres), to expand the arterial passageway.

[0003] In a certain percentage of cases, a dilated arterial wall willcollapse upon deflation of the dilation balloon or will slowly narrowover a period of time. To solve this problem, after the initialexpansion of the artery, the dilatation catheter is removed and a seconddilatation catheter equipped with a stent mounted on the dilationballoon is advanced through the guiding catheter and positioned acrossthe arterial lesion. Once in position the balloon is inflated, expandingthe stent and implanting it in the arterial wall. The expanded stent isleft in place and supports the interior wall of the artery and therebyprevents arterial collapse or narrowing of the artery over time.

[0004] Generally, stents are small tubular metallic structures designedfor intravascular placement within an artery. A typical stent-deliverysystem for balloon expandable stents is characterized by a catheterequipped with a dilation balloon and a stent mounted on the balloon. Insuch a system, the stent is slipped over a folded catheter balloon andcrimped in place. A stent crimped onto a catheter balloon is dependanton friction to hold the stent in position and is therefore subject toslippage while being advanced through the patient's vasculature.Occasionally, during advancement, a stent will slide off of a catheterballoon and migrate within a patient's vasculature necessitatingemergency removal procedures. This condition most often occurs in smallor heavily occluded arteries where contact with either the arterial wallor the lesion to be treated forces the stent off of the catheterballoon. Additionally, sometimes the stent cannot be deployed for avariety of reasons. In these instances, the stent must be able to bepulled back into the guiding catheter without being “stripped off” ofthe stent-delivery catheter.

[0005] What is needed therefore is a catheter with features that providefor improved stent retention. Such stent retention features should serveto prevent contact between a stent and an arterial wall or lesion andshould retain the stent on the catheter balloon if such contact doesoccur. The present invention satisfies these and other needs.

SUMMARY OF THE INVENTION

[0006] The present invention provides an improved balloon catheter fordelivery of stents which includes provisions for stent bumpers. Thebumpers are located adjacent to the proximal and distal ends of thecatheter balloon and form a pocket within which a stent crimped onto thefolded balloon is mounted. The bumpers have sufficient height such thatthe crimped stent does not protrude above the bumpers. Therefore, thestent will remain securely mounted in the pocket formed between thebumpers and cannot slide off the catheter balloon should the stentinadvertently contact the walls of an artery. Additionally, since thecrimped stent is recessed within the pocket formed by the bumpers, thelikelihood of undesired contact between the stent and an arterial wallor lesion is significantly reduced. In a preferred embodiment, the stentbumpers are formed from a soft pliable material, such as polyamide andpolyurethane, in order to minimize the possibility of inflicting traumaupon the walls of the artery during deployment of the stent deliverycatheter.

[0007] Other features and advantages of the present invention willbecome more apparent from the following detailed description of theinvention, when taken in conjunction with the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a side view, partially in cross section, of a particularembodiment of the improved stent-delivery catheter of the presentinvention, the catheter being shown in its pre-deployed position;

[0009]FIG. 2 is a side view, partially in cross section, of the improvedstent-delivery catheter of FIG. 1, the catheter being shown in itsdeployed position;

[0010]FIG. 3 is a side view, partially in cross section, of a particularembodiment of the improved stent-delivery catheter of the presentinvention, the catheter being shown in its pre-deployed position;

[0011]FIG. 4 is a side view, partially in cross section, of a particularembodiment of the improved stent-delivery catheter of the presentinvention, the catheter being shown in its pre-deployed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] With reference to FIGS. 1 and 2, a preferred embodiment of animproved stent-delivery catheter 10, in accordance with the presentinvention, is shown. The catheter 10 comprises an elongated cathetershaft 12 having a proximal end (not shown) and a distal end 13, with aninflation lumen 15 and a guidewire lumen 16 extending therebetween. Thecatheter 10 also includes an expandable member, such as an inflatableballoon 18, mounted on the distal end of the shaft 12, along with afirst stent bumper 22 mounted proximally from the inflatable balloon 18,and a second stent bumper 20 mounted distally from the inflatable member18. The inflatable balloon 18 includes a proximal skirt 17 and a distalskirt 19, which are attached to the catheter shaft 12. FIG. 1 depictsthe inflatable balloon 18 of the catheter 10 in its pre-deployed stateor collapsed state, with a stent 1 mounted thereon. FIG. 2 depicts theinflatable balloon 18 of the catheter 10 in its expanded state.

[0013] The stent bumpers 20 and 22 include openings 34 and 36, which maybe in slip fit or interference fit relationship with the catheter shaft12. The stent bumpers also include intermediate openings 30 and 32respectively, for receipt of the proximal skirt 17 and distal skirt 19of the balloon 18. The bumpers 20 and 22 further include cylindricaloutside surfaces 26 and 24, which are sized to be larger then theoutside diameter of the stent 1, when the stent 1 is crimped onto thecatheter balloon. The stent bumpers 22 and 20, thus provide for moresecure stent retention on the catheter balloon 18. The bumpers preventthe stent 1 from slipping off the balloon 18 during stent placementwithin a patient's vasculature and further serve to protect the stentfrom undesirable contact with arterial walls or lesions, during theplacement procedure.

[0014] The embodiment of the present invention depicted in FIGS. 1 and2, wherein the stent bumpers 20 and 22 are discrete components, isadvantageous in that the stent bumpers may be made of a materialdifferent from the catheter shaft 12. In situations where the risk oftrauma to the arterial walls is high, it is desirable to make the stentbumpers 20 and 22 from soft, pliable, polymers which protect thearterial walls from trauma. Suitable materials are polyamide andpolyurethane. While these materials possess softness and pliability,they typically do not possess the combination of strength, stiffness,and flexibility required for use in the catheter shaft 12. Therefore,where the risk of trauma to arterial walls is high, the embodimentdepicted in FIGS. 1 and 2 may be preferred.

[0015]FIG. 3 shows another preferred embodiment of the catheter of thepresent invention. In this embodiment, the stent bumpers 20 and 22 areintegrally formed with the catheter shaft 12, thereby eliminating theneed to mechanically secure the bumpers to the shaft. The first andsecond stent bumpers 22 and 20 include radial grooves 38 and 39 forreceipt of the proximal and distal skirts 17 and 19 of the catheterballoon 18. FIG. 3 depicts the catheter balloon 18 in its pre-deployedstate with a stent 1 mounted thereon. The primary advantage of theembodiment depicted in FIG. 3 is the simplification in manufacturingthat results from forming the stent bumpers 20 and 22 integrally withthe catheter shaft 12.

[0016]FIG. 4 shows a variation of the embodiment shown in FIG. 3. InFIG. 4, the proximal and distal skirts 17 and 19 of the balloon 18 arefastened to the respective outside diameters 26 and 24 of the stentbumpers 22 and 20. This variation further simplifies manufacturing ofthe device.

[0017] The components of the catheter of the present invention can beformed from a wide variety of conventional materials. The catheter shaft12 and the stent bumpers 20 and 22 may be made by extruding polymericmaterials such as polyethylene, polyvinyl chloride and nylon. Othermaterials such as polyethylene terephthalate and polyester are alsosuitable. The stent bumpers also may be made by injection moldingtechniques. The inflation balloon 18 may be made by blow molding orextruding polymeric materials such as polyamide, polyester, polyolefin,and polyurethane. Other materials and techniques known in the art arealso suitable. The balloon 18 and stent bumpers 20 and 22 may beattached to the catheter shaft by any conventional means such as heatwelding, solvent welding, ultrasonic welding, or adhesive bonding. Othertechniques are also suitable.

[0018] The dimensions of the catheter of the present invention generallyfollow the dimensions of conventional intravascular catheters. Forcoronary use the catheter shaft 12 is typically about 135 cm in lengthwith a maximum outside diameter of about 0.75 mm to 1.5 mm. Stents foruse in coronary applications typically have a crimped diameter of about1.0 to 1.5 mm. Therefore, the stent bumpers 20 and 22 have acorresponding outside diameter of 1.0 to 1.6 mm. Generally, thepreferred stent bumper outside diameter is about 10% greater than thatof the stent 1 to be crimped onto balloon 18.

[0019] The use of the stent delivery catheter shown in FIGS. 1-4generally follows conventional PTCA practices with over-the-wire typedilatation catheters. A guidewire (not shown) is backloaded into theguidewire lumen 16 of the catheter shaft 12 and both the guidewire andthe stent delivery catheter 10 are advanced together through a guidingcatheter (not shown) which has been previously disposed within thepatient's arterial system. The distal end of the guiding catheter isseated within the ostium of the artery targeted for treatment, so that,when the delivery catheter-guidewire assembly is advanced through theguiding catheter, the delivery catheter exits directly into the desiredartery. The guidewire is usually advanced into the patient's coronaryartery until it crosses the lesion to be dilated. Subsequently, thestent-delivery catheter 10 is advanced over the guidewire until theballoon 18 on the catheter 10 is properly disposed within the stenoticregion of the patient's artery. Upon proper positioning across thelesion, the balloon is expanded, thus dilating the lesion and implantingthe stent 1 within the artery. In some situations, the stenotic regionwill be pre-dilated before introduction of the stent-delivery catheter10.

[0020] When a prior art stent-delivery catheter is advanced across thestenotic region, stent contact with the lesion typically occurs whichcreates the possibility of stent slippage on the catheter balloon. Ifthe stent slips proximally, the stent delivery catheter must bewithdrawn and a new catheter inserted, thereby prolonging the stentplacement procedure which may lead to adverse effects on the patient. Ifthe stents slips distally off of the balloon, the stent may migratewithin the patient's vasculature necessitating emergency removalprocedures which generally have an adverse effect on the patient. Withthe catheter of the present invention 10, the stent bumpers 20 and 22constrain the stent 1 from either proximal or distal slippage, thuseliminating the problem of stent slippage and its associated risks tothe patient. Further, the stent bumpers 20 and 22 tend to protect thestent 1 from contact with the lesion which reduces both stent slippageand the undesirable possibility of emboli formation. Emboli areparticles of the lesion which may be formed by abrasion with the stent.Embolic particles are undesirable in that they flow freely within thepatient's vasculature and may cause blockages in other blood vesselswithin the patient.

[0021] It will be appreciated that an improved stent-delivery catheterhas been presented. While only the presently preferred embodiments havebeen presented in detail, as will be apparent to those skilled in theart, modifications and improvements may be made to the device and methoddisclosed herein without departing from the scope of the invention.Accordingly, it is not intended that the invention be limited except asby the appended claims.

What is claimed:
 1. A catheter for the delivery of a stent comprising: an elongated catheter shaft having proximal and distal ends, with an inflation lumen extending therebetween; an expandable member located proximal to the distal end of the catheter shaft, which is in fluid communication with the inflation lumen; and a first bumper and a second bumper positioned adjacent to the proximal and distal ends of the expandable member respectively, the bumpers being secured to the catheter shaft, wherein the area between the first and second bumpers form a pocket for receipt of a stent.
 2. The delivery catheter of claim 1 , wherein the bumpers are integrally formed with the catheter shaft.
 3. The delivery catheter of claim 1 , wherein the bumpers are discrete components which are mechanically secured to the catheter shaft.
 4. The delivery catheter of claim 3 , wherein the bumpers are made from a soft, pliable material.
 5. The delivery catheter of claim 4 , wherein the material used to form the bumpers is polyamide.
 6. The delivery catheter of claim 4 , wherein the material used to form the bumpers is polyurethane.
 7. The delivery catheter of claim 1 , wherein the respective first and second bumpers have an outside diameter which is greater than the outside diameter of a stent crimped over the inflatable member.
 8. The delivery catheter of claim 1 , wherein the stent bumpers are cylindrical.
 9. The delivery catheter of claim 1 , wherein the inflatable member is a dilatation balloon.
 10. The delivery catheter of claim 1 , wherein the respective first and second bumpers are made from an elastomeric material.
 11. The delivery catheter of claim 10 , wherein the elastomeric material is polyurethane.
 12. The delivery catheter of claim 10 , wherein the elastomeric material is polyamide. 